The invention relates to a method for introducing recesses into the surface of a rolling roller for a rolling press.
In order to comminute granular and brittle material to be ground, it is known practice, instead—as conventional—of using shear stress, to comminute the material to be ground economically in terms of energy just by using high pressure in a roller gap. This manner of comminuting has, in addition to the favorable use in terms of energy, the advantage of an increased service life of the rollers used for generating the pressure in the roller gap.
However, in the case of comminuting rock and very hard and abrasive clinker, a predetermined limit is placed on the service life of a roller of a rolling press, this limit resulting from the high degree of abrasion by the material to be comminuted. In the case of comminution in the roller gap, it is additionally important that the material to be ground passes through the roller gap in a uniform and controlled manner For reduced abrasion and for improved and uniform entry of the material to be ground into the roller gap of the rolling press, it is now common practice to profile the counterrotating rollers of the rolling press. In the simplest case, this profiling comprises longitudinal grooves extending in the axial direction on the surface of the roller, compacted material to be ground collecting in these grooves so as to form an autogenous wear protection layer, which results in more uniform entry of material, even when the material to be ground has a broad grain size distribution or a grain size distribution that varies on average over time.
The structure of a roller for a rolling press typically comprises a main roller body with shafts arranged thereon. No particular requirements in terms of material properties are imposed on the main body. A bandage having the surface condition mentioned at the beginning is then shrunk onto this main body or fastened thereto by other means known to a person skilled in the art. This bandage is a substantially cylindrical hollow body, the inner side of which is compatible in terms of size with the main roller body, the outer side of the bandage bearing profiling that is usually applied subsequently. The profiling is generally introduced either by machining, or deposition welding is used to apply weld beads to the surface, with the result that the grooves that produce the profile of the bandage arise between the weld beads. The choice of processing operation for profiling depends essentially on the material properties of the surface of the rolling roller or of the bandage for the rolling roller. Particularly hard materials, such as carbon steels, are generally temperature-sensitive. Cast steel, such as ADI (austempered ductile iron), the microstructure of which changes only with high levels of stress and which only then becomes very hard as a result, can change, even at temperatures around 400° C., to a phase which no longer has the desired material properties and therefore generally becomes very soft and susceptible to wear. Furthermore, cast steels are difficult to weld, and so a weld bead can be applied to the surface only with a great deal of experience, if at all. In the case of machining, depending on the material properties, the material can shear or break off at the surface, or, during machining, the material can heat up undesirably in the regions that are not to be removed, with the result that, during use, the material is subject to high wear at the location where it is not intended to be removed.